digital audio hacks

It seems a reasonable assumption that anyone who’d be willing to spend a few hundred dollars on a pair of headphones is probably the type of person who has a passion for high quality audio. That, or they work for the government. We’re fairly sure [Daniel Harari] falls into that former category though, given how much thought he gave to adding a decent microphone to his Sennheiser HD650 headphones.

Not happy with the results he got from microphones clipped to his shirt or mounted on a stand, [Daniel] realized what he really wanted was a sensitive boom microphone. This would be close enough to his mouth that it wouldn’t pick up stray noises, but at the same time not obstruct his field of view or otherwise get in the way.

He found a few options on the market which would allow him to mount a boom microphone to his HD650’s, but he didn’t want to stick anything to them and risk scratching the finish so those weren’t really an option. [Daniel] decided to go the DIY route, and eventually settled on a microphone that would mount to the headphone’s existing connector which plugs in at the bottom of the cup.

To make his mount, he 3D printed a two piece clamp that could be screwed together and securely attach to the connector without making any permanent changes. Once he had that base component printed, he salvaged the flexible metallic neck from a cheap USB light and used that to hold the female 3.5mm connector. Into that he’s plugged in a small commercially available microphone that is usually used on voice recorders, which [Daniel] said sounds much better than even the larger mics he had tested.

Finally, he used Sugru to encapsulate the wires and create a flexible strain relief. The whole assembly is very light, easily movable, and perhaps most importantly, didn’t require any modifications or damage to a pair of headphones which have a retail price that could double as a car payment.

You’d be forgiven for not realizing there’s still a diehard group of people out there carrying around dedicated MP3 players. While they were all the rage a decade or so back, most consumers have since moved over to using their handy dandy pocket supercomputer for playing their music. Plus controlling every other aspect of their personal life and finances, of course. Though that’s another story entirely.

But as [Conno Brooks] explained to us, there’s a sizable group of open source fanatics who prefer to store their jams on devices running the Rockbox firmware. Only problem is, some of the desirable Rockbox-compatible players are from the Golden Age of dedicated players, and aren’t getting any younger. In a recent blog post, he briefly goes over his ultimately successful attempt to put a new-made battery into his Sansa Clip+, a particularly desirable player that was released in 2009.

There are a few problems with the procedure that has kept it from being very widespread, according to [Conno]. For one, the Sansa Clip+ is tiny and not easily disassembled without destroying it. Worse, the diminutive 30mm x 36mm x 3mm OEM battery is effectively unobtainium. But ironically he was able to find an even smaller battery which seemed like it should work, assuming he could get it wired up.

The OEM battery on the Clip+ uses three wires, which [Conno] presumed was part of some thermal protection system. He first tried to take the circuit board off the original dead battery and graft it onto the modern cell, but something must have tripped because the resulting Franken-pack didn’t output any voltage. On his second attempt he simply ignored the third wire, and luckily the Clip+ didn’t seem to complain and started up as expected.

[Conno] says there’s some careful flexing required to get the new pack installed and the Clip+ closed properly, and the device’s runtime is somewhat diminished by the new battery’s lower capacity. But if it means another few years of keeping Big Brother out of your digital media habits, he figures it’s a worthy trade.

There was a time when any hi-fi worth its salt had a little row of sliders on its front panel, a graphic equalizer. On a hi-fi these arrays of variable gain notch filters were little more than a fancy version of a tone control, but in professional audio and PA systems they are used with many more bands to precisely equalise a venue and remove any unwanted resonances.

On modern hi-fi the task is performed in software, but [Grant Giesbrecht] wanted an analogue equalizer more in the scheme of those fancy tone controls than the professional devices. His project makes for a fascinating foray into analogue filter design, as well as an understanding of how an equalizer combines multiple filters. Unexpectedly their outputs are not mixed because it proves surprisingly difficult to ensure all the filters have the same gain, instead they are in series with the signal path passing through all filters.

The resulting equalizer is neatly built upon a PCB with a 4-AA-cell power supply, and makes for a self-contained audio component. Unexpectedly such analogue equalizer have been few and far between here at Hackaday so it’s particularly pleasing to see. We’re more used to graphical displays for off-the-shelf devices.

A stereo setup assumes that the listener is physically located between the speakers, that’s how it can deliver sound equally from both sides. It’s also why the receiver has a “Balance” adjustment, so the listener can virtually move the center point of the audio by changing the relative volume of the speakers. You should set your speaker balance so that your normal sitting location is centered, but of course you might not always be in that same position every time you listen to music or watch something.

[Vije Miller] writes in with his unique solution to the problem of the roving listener. He’s come up with a system that can adjust the volume of his speakers without having to touch the receiver’s setup, in fact, he doesn’t have to touch anything. By leveraging configurable voice control software running on his computer, his little ESP8266-based devices do all the work.

Each speaker has its own device which consists of a NodeMCU ESP8266 and X9C104 digital potentiometer inside of a 3D printed case. The audio terminal block on the gadget allows him to connect it inline between the speaker and the receiver, giving [Vije] the ability to adjust the volume through software. The source code, which he’s posted on the Hackaday.io project page, uses a very simple REST-style API to change speaker volume based on HTTP requests which hit the ESP8266’s IP address.

The second part of the project is a computer running VoiceAttack, which lets [Vije] assign different actions based on what the software hears. When he says the appropriate command, the software goes through and fires off HTTP requests to the nodes in the system. Everything is currently setup for two speakers, but it shouldn’t be too difficult to expand to more speakers (or even rooms) with some adjustment to the software.

With all due respect to the hackers and makers out there that provide us with all these awesome projects to salivate over, a good deal of them tend to prioritize functionality over aesthetics. Which isn’t a bad thing necessarily, and arguably better than the alternative. But for many people there’s a certain connotation around DIY, an impression that the final product is often a little rough around the edges. It’s usually cheaper, maybe even objectively better, but rarely more attractive.

Which makes builds like this absolutely beautiful 3D printed Bluetooth speaker by [Ahmsville] especially impressive. Not only did he engineer a fantastic sounding speaker that projects stereo sound no matter where you are in the room, he clearly gave a lot of thought into making the final product look as good as it sounds.

The 3D-printed enclosure provides separation for the four internal speakers and two passive radiators, as well as holding the electronics. A custom made 3S battery powers the Bluetooth module though an isolated step-down module, and the twin 18 W TDA2030 amplifiers feed their respective pair of drivers.

The device is surrounded by an impressively detailed 3D-printed mesh, which is then wrapped with some speaker grill fabric to give it a very professional look. In the video after the break, [Ahmsville] shows a time-lapse of building the speaker, as well as a demonstration of how it sounds on his desk.

Whether or not you personally like the concept of the AirPod Bluetooth headphones is irrelevant, as an Apple product one thing is certain: all the cool kids want them. That also means that plenty of overseas manufacturers are pumping out janky clones for a fraction of the price for those who are more about the Apple look than the Apple price tag. Are they any good? No, of course not. But that doesn’t mean you can’t do something interesting with them.

As you might imagine, the left and right “AirPod” each has its own battery, Bluetooth receiver, and speaker. It has to, as they have no physical connection to each other. That also means that each receiver is only playing one channel, making them useless individually. What [Igor] realized was that he could put together a little PCB that combines the two audio channels back into a regular stereo 3.5 mm audio jack.

While he was at it, he also wired the individual buttons on each headphone to a center button on the PCB which would allow him to physically synchronize them. Even still, [Igor] mentions that occasionally they don’t come on at the same time. But what do you expect for something that’s nearly a 20th the price of the original?

We aren’t suggesting you go digging through the trash looking for empty cans, but if you’ve already got some empty cans in the privacy of your own home, you could certainly do worse than turning them into unique enclosures for your electronics projects. Better than sitting in the landfill, surely.

The key to this build is the 3D printed “skeleton” that holds the speaker and circuit board in place. An especially nice touch is how [Robin] designed the mount for the speaker: as it had no flange to attach to, he made a two piece clamp that screws together around the rear of the speaker and holds it in place.

You may wonder why somebody who’s clearly as well versed in CAD and 3D printing as [Robin] is might want to use an empty can as an enclosure; surely he could just design and print a case? Undoubtedly. But the goal here is to reuse what would otherwise be trash, and that occasionally means taking the “scenic” route as it were.